The prior art is replete with concrete construction cable tensioning systems. These systems include both pre-stressed and post-tensioned cables and wire rope. Engineering in the post-tensioning of concrete is a well developed technology and the utilization of such tendons extending through a concrete slab or beam is conventional. The tendons provide structural strength for the concrete in a manner and at a cost not heretofore possible with conventional rebar construction. Utilization of such tendons does, however, require anchor assemblies on opposite ends thereof and the termination of the cable itself at the anchors. The anchor assembly secures the ends of the terminated tendons extending through the concrete bed whereby the tendons remain taut and effective during the life-span of the construction. The effectiveness requires the protection of the terminated tendons, which are usually made of steel or the like, from corrosion. Corrosion forces are well known to cause deterioration in the strength of the concrete if allowed to jeopardize the integrity of tensioning members. To prevent corrosion of the tendon, the steel fibers are usually sheathed in a plastic membrane throughout the length of the slab. The membranes do, however, require termination at the point where the tendons are secured within the anchor assemblies. The reason is obviously to provide appropriate structural integrity at the secured portion.
In the process of post-tensioning, it is important that the tendon is free to move within the hardened concrete so that the tensile load on the tendon is evenly distributed along the entire length of the structure. Methods used to ensure that the tendons provide free movement within the hardened concrete include laying a number of strands of wire in a sheath. It is within this sheath that the strands of wire are stressed after the concrete is hardened. After stressing, the wires exposed from the ends of the anchor assemblies are then cut-off or terminated.
During such post-tensioning of a concrete structure, it is known to insert an end of a cable, usually referred to as a "tendon", into a tapered passage extending through a cable anchor, and then to secure the cable to the cable anchor by means of wedges inserted into the tapered passage into engagement with the cable. However, before the insertion of the wedges, it is necessary to strip the sheath from the end portion of the cable. So as to preserve the "encapsulated" condition of such anchor assemblies and such cable, it is desirable to terminate the sheathing of the cable at appoint just rearward of the end of the wedges within the tapered bore of the anchor. As such, a more effective enclosing of the steel strands of wire within the cable is achieved.
U.S. Pat. No. 5,632,088, issued on May 27, 1997, to Naso et al., for a cable stripper device. The purpose of this cable stripper device is to allow for the stripping of the sheathing from the cable at a location just rearward of the end of the wedges within the tapered passage of the anchor. This cable stripper device has an elongate cutter on a tubular body. The cable stripper has a cutter at one end thereof with an inwardly projecting transverse cutter blade. The cutter and the tubular body are connected so as to allow the cutter to move relative to the tubular body. The tubular body is insertable into the tapered passage of the cable anchor. The tubular body has a frusto-conical surface so as to wedge the cutter blade into penetrating engagement with a sheath on the cable. The cutter blade is hingedly connected to the tubular body so as to be capable of moving inwardly and outwardly relative to the relative position of the end of the tubular body within the tapered passage of the anchor. The cutter blade is positioned at an end of this angular arm.
Unfortunately, with this device, in order to achieve the proper "cutting" effect, it is necessary to first insert the tool into the tapered passage of the anchor. When the tool has been inserted as far as possible into the tapered passage, it is necessary to hammer the opposite end of the tubular body so as to cause the cutter blade to "plow" through the plastic of the sheathing of the cable. When the exterior of the tapered portion of the tubular body is in surface-to-surface contact with the inner wall of the tapered passage of the anchor, the tool can then be rotated so that the cutter blade creates a cut through the sheathing which is transverse to the longitudinal axis of the cable.
Unfortunately, because of the strong forces that are required, the cutter blade must be formed of a hardened steel material. The arm having the cutter blade attached thereto must be machined and strongly affixed to the tubular body. The effort required to hammer the tubular body and to "plow" through the plastic can be extreme at times. As a result, workers will tend to take a more expedient approach and simply rotate the tool at an improper location before the desired position within the tapered passage of the anchor. As a result, the sheathing may remain in those areas which are to be exposed to the wedges. The effect of "plowing" through the plastic material of the sheathing in a longitudinal direction along the cable quickly causes the sharpness of the cutter blade to deteriorate. Furthermore, the tubular body of the tool requires that the entire tool be threaded over the exterior of the cable. Since the cable, in intermediate anchorages, can extend for a relatively long distance, a great deal of labor is required to properly "thread" the cable through the interior of the tubular body.
It is an object of the present invention to provide a method and apparatus for stripping the sheathing from a cable which grips the cable in an easier and more effective manner.
It is another object of the present invention to provide a method and device which allows the tool to be attached easily at any location adjacent to an intermediate anchorage of a post-tension system.
It is another object of the present invention to provide such a device which does not require "threading" over the length of the cable.
It is a further object of the present invention to provide such a device which facilitates the insertion of the tool into the wedge cavity of the anchor.
It is still another object of the present invention to provide a cable stripper device which avoids the "plowing" through the material of the sheathing of the cable.
It is still another object of the present invention to provide a tool which minimizes the machining required for the formation of the cutter blade.
It is still a further object of the present invention to provide a cable stripper which is easy to use, relatively inexpensive, and easy to manufacture.
These and other objects and advantages of the present invention will become apparent from a reading of the attached specification and appended claims.